Gregory: notharctus, an American eocene primate 



151 



The second milk molar (dp^) is much simpler in form ; it is widely triangular in section with a long 

 outer side supported by two widely separated roots, and a low internal protocone spur, supported by a 

 single but large root. It has only a single, high external cusp (paracone), low para- and metastyles and 

 an incipient oblique protoloph-cingulum. The posterolingual face of the tooth is worn by the high pro- 

 toconid face of dnis. The crown of p^ is pushing itself between the inner and the outer roots of dp^, 

 while the crown of p^ lies between the roots of dp'* and dp^ Dp^ distantly resembles that of Adapis 

 in its triangular contour; it has, however, but one external cusp while that of Adapis has two; and its 

 protocone and protoloph are much less developed. Dp" is an extremely simple tooth, somewhat resem- 

 bling the first permanent premolar (p^) but with a shorter crown. It is asymmetrical in all views, with a 

 very short crista anterior, a long crista posterior and a slightly recurved tip. Its anterolingual face fore- 

 shadows the corresponding face of the paracone; its larger posterolingual face is flattened or concave; 

 its external face strongly convex. The anterointernal cingulum faintly foreshadows the protoloph and 

 ends anteriorly in a barely perceptible parastyle; the posterointernal cingulum is homologous with the 

 posterior cingulum of succeeding teeth and ends externally in a low metastyle. The corresponding tooth 

 of Adapis parisiensis has a compressed oval crown, with but little differentiation of parts. (Plate XLII, 

 figs. 6, 7.) 



The lower deciduous cheek teeth are partly preserved in Notharctus tyrannus? Amer. Mus. No. 13029, 

 from the Bridger Basin, Horizon Bo. Unfortunately the surfaces of the crowns are mostly broken off; 

 but the lower parts of the crowns and the roots remain, and beneath them lie the unerupted p4, p3, p2. 

 Behind the deciduous series nii, nio are fully in place, while nis is nearly up. P2 lies nearer to the surface 

 than p3, p4 and would erupt before them. (Plate XLII, figs. 9, 10.) 



Fig. 47. Lower jaw with deciduous and permanent teeth of Adajns parisiensis. After Stehlin. 



1. A. Second right lower deciduous molar. Natural size. 



B. Left mandibular ramus with alveoli of both the deciduous and the permanent incisors, of the deciduous canine, of the first per- 

 manent premolar ("P4"), of the last deciduous molar and first true molar. The other two deciduous molars are in situ. 



2. Lower jaw of Adapis parisiensis, showing all three true molars in place, along with the deciduous molars, the deciduous canine and the 



first premolar. 



The last deciduous molar (dp4) was znuch more molariform than the tooth which replaced it (P4), 

 since its talonid was larger than its trigonid, w^hereas the reverse is the case in p4. The posterointernal 

 root of dms rests in the small talonid basin of p4, while its anterointernal root was apparently in process 

 of resorption. The other deciduous molars (dps, dpo) were likewise elongate anteroposteriorly, their 



